1. Field
Disclosed herein is a method for bonding two or more bonding partners. The bonding partners may be, for example, permanent magnets or magnetizable bodies pocketed in a substrate, e.g. a substrate body of a rotor to be produced, for instance where used, among other things, as the rotor of a permanent magnet synchronous machine (PMSM).
2. Description of Related Art
Bonds of this kind involving two or more bonding partners are often exposed to high mechanical and/or thermal stress, whilst rotors of this kind are often run at high speeds, for example, exceeding 5,000 rpm, resulting in correspondingly high centrifugal forces further stressing the bond.
Producing a durable bond usually involves metering a liquid adhesive, for example a single or two-component resin into pockets of a substrate body mainly consisting of a laminated sheet metal core, after which the magnets are pressed into the liquid adhesive so that each magnet is pocketed in the substrate enveloped in adhesive.
This technique has, however, a number of disadvantages. For one thing, in order to meter the adhesive, each and every pocket has to be accessed with a metering needle. In addition to this, metering is problematic because of the tight tolerances on the dimensions of the pockets. When not enough adhesive is injected in a pocket, the magnet fails to be totally enveloped, resulting in gaps forming between the laminate and the magnet in which corrosion can form. On the other hand, when too much adhesive is injected the weepage adhesive emerging from the gap between the pocket and the substrate body needs to be removed so that the finished rotor has no accumulation of adhesive in the region of the pocket opening.
For another thing, there is the problem of the adhesive shrinking, when cured, to such an extent that stress can rupture the bond when the resulting device is used at high speeds.
An alternative known technique for locating magnets in such a substrate body is to equip the empty pockets of the substrate body with magnets before impregnating the pockets in place with resin. The trouble here is, however, that the impregnating resin needs to be cured hot, refluidizing the already solid but still uncured impregnating resin, causing it to run out of the substrate body in part, forming dribble that needs to be sanded off of the surface of the body.